This invention relates to seating units, and more particularly to seating units in which the seat rises to aid a handicapped or infirm person in both sitting and rising.
Persons who are weak or debilitated, such as the aged, infirm, handicapped and rehabilitating, have some difficulty in reaching a sitting posture in a chair, and substantially greater difficulty in rising from the chair. Consequently, many different systems have been proposed to aid such persons, including power driven mechanisms which raise the entire upper body of an upholstered chair in a lifting and tilting motion. Power driven systems, however, whether electrically, hydraulically or pneumatically driven, are subject to power failure, and tend to be heavy and expensive. In recognition of this or other factors, a number of other configurations for elevating a seat have also been devised. A number are based upon the use of a linkage or parallelogram structure between a seat base and the seat cushion, with the arms of the linkage being of different lengths and therefore tilting the seat as it rises. These arrangements usually employ a power drive extending angularly up from the base. Some mechanisms utilize energy storage devices, such as mechanical springs or gas springs to store mechanical energy. Thus the energy made available when the body weight lowers the seat can be stored and returned to aid in lifting. However, these mechanisms are typically not readily adjustable so as to accommodate persons of different weights, and also tend to be bulky and mechanically complex.
No seat elevator and lowering devices are presently known which provide a suitable combination of low cost, ease of adjustment for different body weights, compactness, energy storage, and capability for use in a variety of modes. It is desirable, for example, to be able to utilize the seat lifting capability in different types of chairs, such as folding and non-folding chairs, to have a unit which is light enough to be portable. Preferably, the unit should be passive and not require an independent source of power. Further, a seat elevating mechanism that is a self-contained unit that can be placed on other surfaces as required can be very useful.